Optimal and Secure Measurement Protocols for Quantum Sensor Networks

TL;DR

This paper extends quantum metrology to networks, deriving bounds for non-local measurements and proposing optimal protocols using GHZ and spin-squeezed states for enhanced sensitivity.

Contribution

It generalizes the Heisenberg limit to quantum networks and introduces an optimal measurement protocol utilizing entangled states.

Findings

Derived a bound based on multi-parameter quantum Fisher information.

Proposed a protocol using GHZ and spin-squeezed states.

Showed the protocol saturates the bound with GHZ states.

Abstract

Studies of quantum metrology have shown that the use of many-body entangled states can lead to an enhancement in sensitivity when compared to product states. In this paper, we quantify the metrological advantage of entanglement in a setting where the quantity to be measured is a linear function of parameters coupled to each qubit individually. We first generalize the Heisenberg limit to the measurement of non-local observables in a quantum network, deriving a bound based on the multi-parameter quantum Fisher information. We then propose a protocol that can make use of GHZ states or spin-squeezed states, and show that in the case of GHZ states the procedure is optimal, i.e., it saturates our bound.